1. Field
Example embodiments relate to silicon substrates, epitaxial structures including the same, and methods of manufacturing the silicon substrates.
2. Description of the Related Art
Many nitride-based semiconductor devices use a sapphire substrate. However, a sapphire substrate is expensive, is difficult for manufacturing chips, and has relatively low electric conductivity. Furthermore, manufacturing a sapphire substrate having a relatively large diameter may be difficult because the sapphire substrate warps at higher temperatures during epitaxial growth due to its relatively low thermal conductivity. In order to prevent or inhibit the above problems, nitride-based semiconductor devices using a silicon (Si) substrate instead of a sapphire substrate have been developed.
Because a silicon substrate has higher thermal conductivity than a sapphire substrate, the silicon substrate does not warp greatly at higher temperatures for growing a nitride thin film, thereby making it possible to grow a thin film having a relatively large diameter on the silicon substrate. However, when a nitride thin film is grown on a silicon substrate, a dislocation density may be increased due to a mismatch in lattice constants between the silicon substrate and the nitride thin film. Consequently, a stress may be generated due to a mismatch in thermal expansion coefficients between the silicon substrate and the nitride thin film.
Also, when a nitride semiconductor is grown on a silicon substrate having a relatively large diameter, a stress may be generated on the silicon substrate at higher temperatures while the nitride semiconductor thin film is being grown. Because the silicon substrate is ductile at higher temperatures, the generated stress may cause plastic deformation of the silicon substrate. As a result, the silicon substrate may become more brittle, and thus cracks may be generated and propagated relatively easily at edge portions of the silicon substrate during a growing process of the nitride semiconductor or a cooling process to room temperature. In some cases, the silicon substrate may fracture due to the cracks and the thermal shock may occur during a fabrication process.